Seeded infiltration and growth of large, single domain Y–Ba–Cu–O bulk superconductors with very high critical current densities
Seeded infiltration and growth of large, single domain Y–Ba–Cu–O bulk superconductors with very high critical current densities
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DOI：
10.1088/0953-2048/18/11/002
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发表时间：
2005-11
影响因子：
3.6
通讯作者：
K. Iida;N. Hari Babu;Y. Shi;D. Cardwell
中科院分区：
文献类型：
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作者：
K. Iida;N. Hari Babu;Y. Shi;D. Cardwell
采用籽晶渗透生长（IG）技术制备了由YBa_2Cu_3O_y（Y-123）超导块材和Y_2BaCuO_5（Y-211）非超导相夹杂组成的单畴Y-Ba-Cu-O（YBCO）单晶。通过这种技术制备的单域在径向方向上的样品收缩率相对较低，为5%，并且与样品尺寸无关，与通过常规熔融加工生长的样品中观察到的收缩率相反，该收缩率随着样品直径的增加而显著增加。此外，通过IG技术生长的样品表现出通常为体积分数的0.9%的低孔隙率，相比之下，在通过常规熔融加工制造的样品中观察到的相应值为约4.9%。对于IG处理的样品，观察到细小的Y-211颗粒嵌入Y-123超导基质中，导致在77.3 K的自场中超过100 000 A cm−2的高临界电流密度Jc。然而，Y-211颗粒在IG样品微结构中的分布是不均匀的（与以前的报道不同），这导致Jc的空间分布的变化。Y-211在籽晶附近（即对应于初始c扇区生长阶段）的体积分数特别地典型地为约5%，相比之下，在更远离籽晶的a生长扇区中的值高达30%（其很好地对应于本文所研究的样品组成的理论值）。Y-211夹杂物的体积分数在c生长扇区更远离种子是约22%。最后，Y-211颗粒在Y-123基质中的分布变化趋势与常规熔体加工生长的样品相似。
Single domain Y–Ba–Cu–O (YBCO) composed of a YBa2Cu3Oy (Y-123) superconducting bulk matrix with discrete, non-superconducting Y2BaCuO5 (Y-211) phase inclusions has been fabricated by a seeded infiltration and growth (IG) technique in the form of cylindrical pellets up to 32 mm in diameter. Sample shrinkage in the radial direction for single domains prepared by this technique is relatively low at 5% and independent of sample size, in contrast to the shrinkage observed in samples grown by conventional melt processing, which increases significantly with increasing sample diameter. Furthermore, samples grown by the IG technique exhibit low porosity of typically 0.9% of the bulk volume fraction, compared with a corresponding value of around 4.9% observed in samples fabricated by conventional melt processing. Fine Y-211 particles were observed to be embedded within the Y-123 superconducting matrix for the IG processed samples, leading to a high critical current density, Jc, of over 100 000 A cm−2 at 77.3 K in self-field. The distribution of Y-211 particles in the IG sample microstructure, however, was inhomogeneous (unlike in previous reports), which leads to a variation in the spatial distribution of Jc. The volume fraction of Y-211 in the vicinity of the seed crystal (i.e. corresponding to the initial c-sector growth stage), in particular, is typically around 5%, compared with a value of up to 30% in the a growth sectors more distant from the seed crystal (which corresponds well to the theoretical value for the sample composition studied here). The volume fraction of Y-211 inclusions in the c growth sector more distant from the seed was around 22%. Finally, a trend of the variation in the distribution of Y-211 particles in the Y-123 matrix grown by the IG technique was similar to that in sample grown by conventional melt processing.